Electron tube and method of making the same



Aug.13,1946. J S,VANSA T 2,405,915

ELECTRON TUBE AND METHOD OF MAKING THE SAME Filed Dec. 15, 1943 .32 JOHN S. VANSANT {y 71137 Quarries a Patented Aug. 13, i946 ELECTRON TUBE AND METHOD OF MAKING THE SAME John S. Vansant, Huntingdon Valley, Pa., assignor, by mesne assignments, to Philco Corporation, Philadelphia, Pa., a corporation of Pennsylvania Application December 15, 1943, Serial No. 514,409 7 Claims. (Cl. .2 o 2'1.5)

This invention relates to electron tubes, and more particularly those of the type having closely spaced electrodes.

In prior electron tubes, difficulties have been encountered in establishing and maintaining the required exact close spacing of the electrodes. For example, in two-electrode tubes in which the electrodes have commonly taken the form of spaced parallel discs, this difiiculty has been encountered. The spacing of such electrodes would vary materially when the elements were heated and on occasions caused short circuiting, particularly if the electrodes became heated beyond their normal. operating temperatures.

It is an object of the present invention to provide an improved electron tube structure, adapted to be readily manufactured in volume with accurately spaced electrodes.

Another object is to provide an improved tube structure in which heating will have little or insignificant effect on the spacing of the electrodes.

Another object is to provide a tube incorporating the foregoing novel characteristics which may be fitted directly into the end of a two-conductor concentric or coaxial cable.

Another object is to provide a simplified and economical method of manufacturing a tube of the foregoing type.

Other objects and advantages of the invention will become apparent as it is described in connection with the accompanying drawing.

In the drawing Fig. 1 is a longitudinal sectional view of an electron tube of the diode-type, embodying the invention, shown in the process of manufacture; and

Fig. 2 is a similar view of the completed tube.

Referring to the drawing, a cylindrical metal tubular member It having a flange l2 at one end is held fixedly during manufacture. A metallic holder 14 of any convenient form, such as a disc, spider or diametric-bar form, is located and secured within the member l0 and supports a hollow cylindrical or tubular cathode l8 whose end I6 is sprayed with a cathode spray of known composition. The cathode is substantially coaxial with the envelope or casing member I0.

An anode comprising a cylindrical tubular member 26, slightly enlarged at its innermost end, is securely mounted at its other end on a short rod-like conductor 22 extending through a glass cap 24 closing one end of the member 10.

To locate the anode, a cylindrical mandrel 26 (Fig. 1) which may be formed of insulating material, is inserted through the cathode l6 and enters thesmallerportion of the anode which is then positioned with its enlarged portion around and accurately spaced a predetermined distance from the cathode. While so held, the anode is sealed in position by fusing the glass at the neck of the cap 24 to the conductor 22 the periphery of the cap having previously been scaled to the metal casing or envelope ID. I

The mandrel may now be withdrawn and a filament or heater element 30 (Fig. 2) of conventional structure may be inserted within the cathode. The heater element 30 may be conventionally supported on conductors extending through a glass press 32 mounted in a glass cap 34 for seal-ing the end of the envelope or casing H3 opposite the anode. J I The tube maybe evacuated in conventional fashion, as for. example by means of the exhaust tubulation tip 36. V p There is thus provided a diode-type electron tube structure having concentric electrodes which are accurately positioned and secured. The structure of the electrodes lends itself to the simple manufacturing method described, en-

, abling large scale production because complicated arrangements for obtaining and maintaining the exact spacing of the electrodes are avoided.

Because of the concentric cylindrical structure of the electrodes, any expansion thereof is effectively confined to a longitudinal direction and does not affect the electrode spacing. In the event, however, that any expansion takes place radially, the electrodes will expand simultaneously and their spacing will be maintained.

Under certain conditions, it is desirable to use a diode-tube with a concentric hollow cable or conductor. In such a case, the diameter of the metal member Ill may be such as to fit within the end of the outer conductor of the cable (not shown) and the anode conductor 22 may abut or connect with the internal cable conductor. The circuit to the cathode will be from the casing l0 through the cathode support or holder I4 to the cathode 18.

In some conditions, the mandrel may be in two parts; and the end or inner part which positions the electrodes may remain in position after the tube is completed.

For simplicity, a tube of the two-electrode or diode type has been illustrated, but it is to be understood that the invention is applicable to other types of tubes.

Modifications within the scope of the invention will occur to those skilled in the art. Therefore the invention is not limited to the specific embodiment shown and described.

I claim:

1. In an electron tube, an envelope comprising a tubular conductive member and end closures therefor composed of non-conductive material, a hollow cathode electrode within said envelope in substantially coaxial relation to the tubular I conductive member, conductive means connecting said electrode to said member, a. conductive element extending through one of the end closures of the tube envelope, and a second hollow electrode attached to and supported by said element, said second hollow electrode being longitudinally adjacent to and in substantial co-axial alignment with said first hollow electrode and having a portion closely encircling a portion of said first electrode.

2. In an electron tube, a tubular electrode supported within the tube, a second tubular electrode having a portion axially adjacent to said first electrode and of substantially the same internal diameter, said second electrode having another portion of larger diameter surrounding a part of said first electrode, and means for supporting said second electrode. i v r 3. An electron tube comprising a container having a cylindrical metallic portion'and a nonconductive portion, a cylindrical cathode supported by said metallic portion, a, conductor extending through said non-conductive portion, a

second cylindrical electrode supported onsaid conductor, said second electrode having a flared end portion, said cylindrical cathode, said conductonand said second cylindrical electrode being longitudinally displaced and'in substantial co-axial alignment with each other and with the cylindrical metal portion of the container, said flared end portion of the second'electrodeoverlapping the end of said cathode,

4. An electron tube as defined in claim 3,1characterized in that all overlapping points of the flared portion of the second electrode are substantially equi-distant from the overlapped end portion of the cathode.

5. An electron tube comprising a container having a cylindrical metallic portion and a nonconductive portion, a tubular cathode supported by and connected conductively to said metallic portion, a conductor extending through said nonconductive portion, a second tubular electrode supported on said conductor and having an enlarged tubular portion telescoping with a portion of said cathode and spaced a predetermined distance therefrom, said conductor, said tubular cathodaand said second tubular electrode all leeing longitudinally displaced and in substantial co-axial alignment with each other and with the cylindrical metallic portion of the container.

6. In an electron tube, an envelope which includes a cylindrical portion and two end portions, a tubular electrode, means for fastening said tubular electrode to the inner wall of the cylindrical portion of the envelope in predetermined co-axial position, a conductor extending through one of the end portions of the envelope and secured thereto, a scond tubular electrode secured to and supported by said conductor and positioned longitudinally adjacent to said first electrode in co-axial alignment therewith, said second electrode having a flared portion which overlaps the end of the first electrode and is substantially equi-distant therefrom at all overlapping points.

7. An electron tube as defined in claim 6, characterizedin that the cylindrical portion of the envelope is of conductive material, the end portions are of non-conductive material, and the means for fastening the first-named tubular electrode to the inner wall of the envelope is a conductive means.

JOHN S. VANSANT. 

